title: Prognostic factors and percutaneous nephrolithotomy morbidity: a multivariate analysis of a contemporary series using the Clavien classification.
abstract: OBJECTIVE
  We stratified factors affecting treatment morbidity, compared the outcomes of percutaneous nephrolithotomy procedures from a single department and provided evidence of treatment benefits when percutaneous nephrolithotomy is performed in an expert setting.
  
  
  METHODS
  Since the department became a dedicated endourological center in 2002 we grouped all percutaneous nephrolithotomy procedures into those performed before 2002 (group 1) and after 2002 (group 2). The modified Clavien classification was used to score morbidity. Independent variables with an influence on complications were studied including stone size, operating time, operative complications, dilation device, urine culture, group allocation and lithotripsy device. Contingency and logistic regression were used for univariate and multivariate analysis.
  
  
  RESULTS
  Of the 244 percutaneous nephrolithotomy procedures 68 comprised group 1 and 176 formed group 2. Statistical preoperative differences were patient age, the use of anticoagulants and positive urinary cultures. Group 1 had a complication rate of 56.8% and group 2 had a complication rate of 37.2%. There were significant differences between the groups (p = 0.007). Almost all complications were grade 1 to 2. On univariate analysis the influence variables were urine culture (OR 1.69), group allocation (OR 2.20), stone size (OR 2.28), dilation device (OR 4.8), lithotripsy device (OR 1.22), perioperative complications (OR 2.83) and surgical time (OR 1.87). On multivariate analysis the independent factors in the complicated outcome were stone size (OR 1.25), type of lithotripsy device (OR 1.35) and incidence of perioperative complications (OR 3.71).
  
  
  CONCLUSIONS
  The dedicated setting for percutaneous nephrolithotomy at our center resulted in decreased operative time, more uneventful procedures and decreased hospitalization time. The modified Clavien morbidity score is a reliable tool for more objective outcome comparisons after renal stone treatment.
authors.affiliation: Department of Urology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. j.j.delarosette@amc.uva.nl
authors.forename: J J M C H
authors.initials: JJ
authors.lastname: de la Rosette
authors.forename: J Rioja
authors.initials: JR
authors.lastname: Zuazu
authors.forename: P
authors.initials: P
authors.lastname: Tsakiris
authors.forename: A M
authors.initials: AM
authors.lastname: Elsakka
authors.forename: J J
authors.initials: JJ
authors.lastname: Zudaire
authors.forename: M P
authors.initials: MP
authors.lastname: Laguna
authors.forename: Th M
authors.initials: TM
authors.lastname: de Reijke
mesh_terms: D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009403:Nephrostomy, Percutaneous / Q000009:adverse effects* / Q000145:classification*; D011379:Prognosis; D012189:Retrospective Studies